Ferromagnetic Behavior and Its Dependence on the Crystal Orientation and on the Method of Demagnetization in Single Crystals and a Polycrystal of 0.5 Percent Aluminium Iron

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概要

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• The magnetization curve, ballistic demagnetizing factor (as defined with respect to the break point of the descending hysteresis curve), N, domain distribution, magnetocrystalline anisotropy constants, K_1 and K_2, as well as K_0, saturation magnetic field, H_s, residual magnetization (as the magnetization at the break point of the descending hysteresis curve), I_k, coercive force, H_c, and initial magnetic susceptibility, X_0, and their dependence on the crystal orientation have been studied at ordinary temperatures, using the ballistic method, with single crystals and a polycrystal of iron containing 0.53% Al in thermally demagnetized (TD) state and in alternating-current demagnetized (AD) state. It has been discovered that, irrespective of either single crystal or polycrystal and of crystal orientation, N_<TD>>N_<AD>>N_a, where N_a is Shuddemagen's demagnetization factor. This fact suggests that the domain distributions in TD and in AD states are different in such a way that, in TD state, the volume of domains magnetized along a direction of easy magnetization far from the rod axis of the specimen is larger than that of domains magnetized along a direction of easy magnetization nearest to the rod axis, as compared with AD state. This may be interpreted by an idea that TD and AD induce additional small uniaxial magnetic anisotropies with positive and negative anisotropy constants, respectively, the former anisotropy being due to directional ordering (the self magnetic-anneal effect), and the latter due to the re-distribution of interstitial foreign atoms. It has been found that (K_0)_<TD>>(K_0)_<AD> and (K_1)_< TD>>(K_1)_<AD>, and that, irrespective of either single crystals or polycrystal and of crystal orientation, A_<TD>>A_<AD> (A=∫^I_s_0HdI), (H_s)_<TD>>(H_s)_<AD>, (I_k)_<TD><(I_k)<AD>, (H_c) _<TD>=(H_c)_<AD>, and (X_0)_<TD>> (X_0)_<AD>. It has also been found that, in single crystals, (H_<s[110]>-H_<s[100]>)_<TD>>(H_<s[110]>-H_<s[100]>)_<AD>>0, and (H_<s[110]>-H_<s[111]>)_<TD>> (H_<s[110]>-H_<s[111]>)_<AD>>0, and (I_k)_<AD>> (I_k)_<TD>>I_s/〓β_i (Kaya's rule), where β_i's (i=1, 2, 3) are the direction cosines, referred to the tetragonal axes, of the rod axis of the single crystal specimen. We have found, further, that (K_2)_<TD> < (K_2)_<AD>, and that, irrespective of the method of demagnetization, 3/2 > K_2/K_1>-3, H_<s[110]>>H_<s[111]>> H_<s[100]>, (H_s)_<poly>>(H_s)_<single>, (I_k)_<poly>>I_s/〓β_i, H_<c[100]><H_<c[110]><H_<c[111]>, (H_c)_<poly>>(H_c)_<single>, X_<0[100]>>X_<0[110]>>X_<0[111]>, and (X_0)_<poly>>(X_0)_<single>. It is shown that the measured facts concerning the difference in the method of demagnetization may be explained by the above-mentioned idea of small uniaxial ferromagnetic anisotropies with negative and positive anisotropy constants, induced, respectively, by TD and AD, and that the observed relations between the polycrystal and single crystal data may be interpreted in terms of the magnetic interaction between crystal grains. It is also shown, for both of TD and AD states, that the observed anisotropy of H_c coincides well with a formula H_c=H_<c[100]>(〓β_i/〓β_i^3), which is derived from Kondorsky-Vonsovsky's theory for the case where the 180°domains are grouped and I_k=I_s/〓β_i (Kaya's rule) and that the observed anisotropy of X_0 accords well with a formula X_0=X_<0[100]> [2(〓β_i^3/〓β_i)-〓β_i^4/(〓β_i)^2], which are derived from Brown's theory of the domain wall displacements for the case where 180°domain are grouped and the relative volumes of domains in unmagnetized state are expressed as v_<i0>=(1/2) ( β_i/〓β_i). Furthermore, it has been found that a formula |K_1|=αI_s(H_s)_<poly>, where α=1/3〜1/4, holds for cubic ferromagnetics.

• 東北大学の論文

著者

• Yamamoto M.

  Research Center For Nuclear Physics Osaka University

• Yamamoto Mikio

  Research Institute For Iron Steel And Other Metals

• MIYASAWA Ryofu

  the Physics Department of Hirosaki University

• Yamamoto M.

  Research Institute for Iron, Steel and Other Metals

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